I was wondering whether the following is a sensor issue: I did a (very) low-light / exposure push test using an admittedly slow lens, 24-105mm F/4.0 L IS. When pushing the exposure of a DNG frame in post, there is a lot of noise, which is to be expected considering it's quite a large exposure push. However, it seems that on top of the noise, the bottom half of the image has a blue-ish tint? Surely that's not normal? (Please disregard the black bit at the top, that's my window frame).

JorgeDeSilva wrote:I'v seen strange noise patterns, banding, etc... but tonight I will shoot a lot of low light scenes, with a 28mm f/2.8 lens and a 50mm f/1.4 lens... let's see...

I guess John Brawley was right to mention the BMCC was not a "low-light" camera. When there is enough light, the image looks absolutely stunning and I realise my test was very extreme and you wouldn't usually do this massive of an exposure pull in post, but the blue tinted bottom half also shows up in dark images when using a faster lens, rather than doing an exposure pull in post (it's even visible on the BMCC LCD screen)

There are also lots of stuck pixels (blue and white mostly it seems). It seems that you can take them out of the footage with chroma noise removal, but I thought the BMCC had a pixel remapping feature?

Frankly, I think you are pushing that a little beyond reason. You are bound to get all sorts of mess when you push an image past what the SNR can handle on any device. Small sensors will always perform worst in low light that larger sensors (of equal technology). There is only so much light they can absorb and signal booster, in any medium, sucks.

It's like driving your car in 6th gear while doing 20 mph and stating that the transmission is making funny noises and the acceleration isn't really as smooth as it is in 3rd. Can the car physically do it? Yes. Was it designed to do it? No.

That's the reason I never understood why Canon/Nikon included the ridiculously high ISOs on their cameras...everyone says the images are all but unusable, but it's cool they can shoot 200,000 ISO! um, no it isn't.

YMMV, but I don't see this as a severe limitation of the camera or anything. Nor do I think there is an issue with your camera, but I'm not BM. Have you sent the image to their tech support?

Using the exact same lens as you, at ISO 800, Raw mode, f4, 1/50 shutter

Boosted in photoshop without any NR or sharpening, (cropped to 2.4)

Look at the noise and the artefacts. It is perfectly normal. These are not night vision cameras. There is no low-light sensor issue. If you try to push the raw image too far when there is not enough light, you will see artefacts from every camera.

I do realise that it's totally normal that there will be noise in the image (and in the image above I have actually removed chroma noise, which is why the noise still looks tons better than in the RAW 5D photograph you posted.)

However, it seems a little off to me that the blue artefacts are only present in the bottom of the image. It's impossible to get rid of with chroma noise reduction. The fact that it starts mid-way through the sensor/image reminds me of this guy's problem: http://www.bmcuser.com/showthread.php?1 ... ra-holders

I do realise that it's totally normal that there will be noise in the image (and in the image above I have actually removed chroma noise, which is why the noise still looks tons better than in the RAW 5D photograph you posted.)

However, it seems a little off to me that the blue artefacts are only present in the bottom of the image. It's impossible to get rid of with chroma noise reduction. The fact that it's horizontally mid-way through the sensor/image reminds me of this guy's problem: http://www.bmcuser.com/showthread.php?1 ... ra-holders

Can you see the difference when shooting something with enough light? ie: normal conditions? If not, I wouldn't worry about it.

Tom wrote:Can you see the difference when shooting something with enough light? ie: normal conditions? If not, I wouldn't worry about it.

I haven't used the camera much yet as I only got it today, but I have seen the issue in more normal conditions as well, in a dark area of the image. I doubt it will show up in daylight. I will keep testing and see whether it will be an issue or not.

Tom wrote:also, didnt you say back in sept that you hadn't pre-ordered yet..... how did you get your camera already???

I bought it off someone who ordered the camera back in April. He is abroad for half a year and "exporting" the camera would have been too expensive, so I paid him and he had CVP send it to my address instead.

Christian Schmeer wrote:I bought it off someone who ordered the camera back in April. He is abroad for half a year and "exporting" the camera would have been too expensive, so I paid him and he had CVP send it to my address instead.

ah, I know the guy, he offered it to me for rental, I asked to buy it, then you offered him more money...... *sigh*

Christian Schmeer wrote:I bought it off someone who ordered the camera back in April. He is abroad for half a year and "exporting" the camera would have been too expensive, so I paid him and he had CVP send it to my address instead.

ah, I know the guy, he offered it to me for rental, I asked to buy it, then you offered him more money...... *sigh*

I'm having the exact same issue. In the viewfinder the shift in exposure is visible along with in my raw files when I go to edit. I didn't have much time to make this video as I just got the camera but here's a link to a video that illustrates a scenario where this would be a definite problem.

EdmondHawkins wrote:I'm having the exact same issue. In the viewfinder the shift in exposure is visible along with in my raw files when I go to edit. I didn't have much time to make this video as I just got the camera but here's a link to a video that illustrates a scenario where this would be a definite problem.

Please download the video to see the problem more clearly

That's definitely visible Looks different to what my issue looks like, but it's in the same spot...

Do you have any white stuck pixels in your RAW low light footage? (I don't mean noise, I mean white dots that don't move in the footage). I seem to remember John Brawley saying the camera had a pixel remapping feature, but it doesn't seem to be doing its job?

I am also wondering whether the noise reduction in Davinci Resolve may be able to get rid of all the problems. I have been using Lightroom so far.

Christian Schmeer wrote:I bought it off someone who ordered the camera back in April. He is abroad for half a year and "exporting" the camera would have been too expensive, so I paid him and he had CVP send it to my address instead.

ah, I know the guy, he offered it to me for rental, I asked to buy it, then you offered him more money...... *sigh*

EdmondHawkins wrote:I'm having the exact same issue. In the viewfinder the shift in exposure is visible along with in my raw files when I go to edit. I didn't have much time to make this video as I just got the camera but here's a link to a video that illustrates a scenario where this would be a definite problem.

Please download the video to see the problem more clearly

When shooting at night at the dark night sky, I would expect to see artefacts.

Another thing: Every once in a while (very rarely though), there is a single frame, which will have some bright dots in it. What could this be? I've noticed this in John Brawley's and Philip Bloom's footage as well, but I can't remember in which videos. I am guessing since it only ever happens to one single frame, it's firmware fixable.

Tom wrote:When shooting at night at the dark night sky, I would expect to see artefacts.

I still think that it's abnormal for any artefacts not to be "spread out" over the sensor. This whole 50/50 thing seems weird to me. EdmondHawkins's issue looks different and seems much more pronounced than mine though.

Yeah, we have seen this before in ultra low light. This further confirms that this is some variety of what is discussed as sCMOS on the Andor and PCO-tech sites. I could only see it with the large downloaded file. So I guess, if you want to shoot in light like that, you will have to put a mask on half the frame and do an adjustment. Quite honestly, this would not bother me in the slightest. I would not use any camera anywhere near where you are operating, in terms of light level. But if you wanted to expose a large portion of the frame to dark stuff like that, and it was for cinematic release where it might show, I would just put a minor curve on half the frame to match it.

I've done some more testing. It seems that we need to feed the BMCC with as much light as possible - better too much, overexpose and pull the highlights back in, than too little and try to pull the shadows back in. Pulling darkness back in (e.g. in a night city scape situation) will expose the sensor's weaknesses, which is to be expected. It's just that the BMCC sensor seems to have that weird 50/50 issue, which still puzzles me. I am wondering if every BMCC behaves this way?

This also makes me think that a lens with a maximum aperture of F/4.0, such as the Canon 24-105mm F/4.0 L IS lens may be somewhat usable for low light on a 5D Mark III, but it is unusable for low light on the BMCC. I tried a similar shot (night cityscape) using a Carl Zeiss 180mm F2.8 lens, ISO 400 and 324 degree shutter angle and it looks much much better! The 50/50 issue is still slightly visible, but not nearly as much as before. It looks more like a dark horizontal line now. I will have to invest in some more fast lenses (F/2.8 or faster). I'd still like BMD to comment on the whole 50/50 issue though...

Christian Schmeer wrote: I'd still like BMD to comment on the whole 50/50 issue though...

The non-BMD non engineer answer for this is that it's a *signature* of the new style of sensor that BMD have chosen to use, the sCMOS.

The reason the sensor performs so well in terms of dynamic range and very high bit depth is because it has a certain kind of structure that means the sensor is kind of processed in two parts. That's my lay understanding.

What you're seeing, when operating at the extremes of under exposure, is slight differences in readouts. It's not exactly a "fault", more just an artefact of the sensor architecture itself, in much the way noise and banding is on others.

As I've said before, the camera is very honest in the pictures that you'll get with it. You're seeing it warts and all.

Perhaps one needs to use more discretion with this camera than those that have more in-camera processing and noise reduction. The BMCC is never going to be a low light demon and these kinds of noise patterns are part of the fundamental structure of the sensor technology itself.

I think Tom's earlier post with a 5Dmk2 at the same exposure says it all. It's got very similar noise and artefacts.

You're going to see the noise and dynamic range limitations of the sensor when you push the image this hard.

You also need to look at what you're doing in that example image. You're seeing the horizontal line, but if you interrogate the image, the majority of it is dark and black. Lifting the blacks isn't going to bring out any more shadow detail because you're already beyond what the sensor can do. If those blacks were actually black not lifted muddy dark grey, I doubt you'd see the issue...

I guess I'm saying that when you try to lift the image beyond the shadow dynamic range, you're going to see these kinds of artefacts. It's like trying to recover whites that have already been clipped in camera.

jb

EDIT:I see also that @DNomer has picked the artefact just by it's visual signature in the earlier post too.

John Brawley wrote:You're going to see the noise and dynamic range limitations of the sensor when you push the image this hard.

You also need to look at what you're doing in that example image. You're seeing the horizontal line, but if you interrogate the image, the majority of it is dark and black. Lifting the blacks isn't going to bring out any more shadow detail because you're already beyond what the sensor can do. If those blacks were actually black not lifted muddy dark grey, I doubt you'd see the issue...

[/quote]

I see your point that pushing the grade will yield issues, but my specific camera see's the issue in every ungraded scenario:In the Viewfinder, looking at the original RAW, and ProRes files

When opening those frames in photoshop, until I have to boost the exposure by more than +1, I cannot see any visible artefact.

Looking at those histograms, It is clear that there is not enough light in the shot.

Hence you are able to bring out the "signature" of the sensor.

I dont normally like to crush my blacks, but when using other cameras (and when playing with this dng) I find that for shots such as the night sky, where noise and artefacts can usually pop up from most cameras, just crushing the blacks a little bit helps to help to clean the image a bit.

You said that this line appeared in every shot, care to share a dng or video of a shot where the image has been exposed more towards the middle of the histogram, or even to the right?

Can you see the artefacts in this shot where I have crushed the blacks slightly?

When opening those frames in photoshop, until I have to boost the exposure by more than +1, I cannot see any visible artefact.

First off, Tom, I want thank you for responding and helping me out with this situation. I know I'm harping over a small aspect of this camera but after waiting as long as we have I wasn't expecting to run into an issue like this and it's really been disparaging.

The shift in the raw file is quite visible to me and everyone else I've shown the raw file to (on multiple screens) including BMD support. Download the clip on vimeo () and you can see the shift better in motion. My complaint is not based on trying to boost this image, it's just in getting a clean image from the start. Just to specify, clean, in this situation, just means no "signature" split.

Tom wrote:Looking at those histograms, It is clear that there is not enough light in the shot.

Hence you are able to bring out the "signature" of the sensor.

With the options available to me, this is the best exposure I could get out of the camera. I want to be able to have the option to have establishing shots at night or scenes where characters are lit well and there's darkness behind them. Do you have any suggestions with the camera on how I could avoid getting the line to show up when Im shooting with available light? Again, I'm not trying to boost the image in post- I'm seeing this "signature" shift in the viewfinder (when I'm filming) and in the raw.

Tom wrote: I dont normally like to crush my blacks, but when using other cameras (and when playing with this dng) I find that for shots such as the night sky, where noise and artefacts can usually pop up from most cameras, just crushing the blacks a little bit helps to help to clean the image a bit.

I have no problem crushing the blacks a little. However, I had the editor on my show take a crack at this sequence and his final look (with crushed blacks) still exposed the "signature" horizontal shift. I'd be happy to claim ignorance on this matter, but having a professional editor, photographer, and motion graphics artist all take a look at the raw (and corrected) and all say something to effect of, "damn," I can't help but feel disappointed in the product. I've tried added an adjustment layer and masked it over the top half of the split to balance out this issue, but this seems like a hacky work around for something that should just deliver pre color correction.

Tom wrote: You said that this line appeared in every shot, care to share a dng or video of a shot where the image has been exposed more towards the middle of the histogram, or even to the right?

Apologies, I meant every shot that involved darkness. In Daylight and well lit scenarios, I am very pleased with the look but I don't want to be restricted to only those conditions.

Tom wrote: Can you see the artefacts in this shot where I have crushed the blacks slightly?

ScreenHunter_06 Jan. 21 12.17.jpg

I will say it looks better, but it's still visible to me. If I were to apply that color correction to that entire scene, you'd still see it clearly as movement exposes this issue. Again, please download the video- you'll see that the raw footage + color corrected samples all show this problem and it's magnified when the camera is moved around as the split exposes the sky differently.

That particular Canon lens 24-105 dont play nice with my Scarlet in low light as well.I would avoid anything lower than 2.8 for future lens purchases.However its a great lens for kicking around during the day.

Thank you for sending Kholi!!! Black Magic said sending me a new camera wouldn't yield different result but this is certainly a different result! I'd be happy with getting what you got out of this camera.

Would you mind sending me a dng from any of those shots? Several if Possible.

Also what lens used, fstop (if possible), asa and shutter angle would be majorly appreciated.

I'll try filming with as similar settings and conditions you have and this can help better prove my point to Black Magic.

Right now all of my RAW's on a drive hangin' out at the office, I'm going there but the internet's HYPER slow, so uploading things is kind of the most frustrating modern experience ever. I'll upload a longer LT from RAW clip that I have, which has ample FPN (Fixed Patterned Noise) which is definitely to be expected, but no static half-screen lines or white pixels to speak of, and I had the camera running for a full day.

There's ONE DNG up there on my Google Drive labeled SK_Night, it's from the same setup. May or may not help.

As far as the lens:

21/2.8 Zeiss ZF or it was a 35/2 Zeiss ZF, one or the other. The only Active lens I've used on the camera was the Sigma 20/1.8. I definitely agree with Eric, that 24-105 would not be the lens I choose, aperture is WAY too slow for the application.

I also wonder if it's not something in the camera talking to the lens (IS, Aperture) that's causing the issue with some of the bodies. There was one job where we used the 70-200/2.8 non IS on the camera but had no issues either, then again we were well lit.

Additional thoughts: I've been using Viewfactor's IDX plate and IDX batteries, again mostly manual glass so no electronic contacts, All are 2.8 or faster. SSDs are mainly OCZ Vertex 3 240G... hmm that's about it.

I would expect variations in how prone to such artefacts each sensor is, it seems slightly less prominent in Kohli's camera.

Personally, I consider this, Edmonds and Christians to be within acceptable parameters. For shots as low light as these, id either use a different camera or adjust my grade to hide it. Obviously its all down to your own personal take on your own working parameters, but my point is that I consider this not to indicative of a fault at all, but simply a result of insufficient light to film with.

EdmondHawkins, have you tried viewing them on a rec709 tv screen? is the artefact as visible? On your ungraded dng, i cannot see it at all on a Sony Bravia screen.

Last edited by Tom on Mon Jan 21, 2013 5:33 pm, edited 1 time in total.

That's FPN, or the actual pattern of the sensor showing up. That's expected.

That's not what the other people are pointing out, what they're seeing is something completely different that actually affects the lower and upper halves of the image independently. The lower's exposure is darker, or/either the upper halve's brighter.

Kholi's DNG looks the best so far, though I believe the blue tinted noise is pronounced in the bottom half, but that might just be because the frame is darker at the bottom. The only way to know for sure is recording something with a solid colour in low light (e.g. night sky).

Any chroma noise will always be more abundant in the lower half of the curve, and more much prevalent the closer you move to 0IRE. That, again, should definitely be expected. Sony cameras are really great and removing it, notably the FS100, but if you pick up a GH2 and do something like this I guarantee you it will not be anywhere near as clean, and the tearing blue or red chroma will drive you out of a window.

xDDD

The line should be in everyone's footage when underexposed, again that's the sensor's pattern showing up. The difference in the top half of the frame and the bottom, that one I don't know about.

Personally, I consider this, Edmonds and Christians to be within acceptable parameters.

Really? And you downloaded the vimeo video i posted and didn't see it there either? Would you mind looking at this through several monitors before making that kind of a judgement call, please? The histogram of Kholi's sample .dng was just as underexposed as mine yet there was no visible line when looking at the raw file. I added his DNG to my Drop Box that contains my samples if anyone else wants to weigh in on if they can see it more easily on my shot vs Kholi's or not. His is labled sk_night.dng https://www.dropbox.com/sh/tp7w1yw3y7yxr9v/2aIHDYgCN_

Tom wrote: EdmondHawkins, have you tried viewing them on a rec709 tv screen? is the artefact as visible? On your ungraded dng, i cannot see it at all on a Sony Bravia screen.

Yes, virtually every type of screen showed this issue at my office (I work for NBC). Are you in a well lit room? If you're looking at it in a room that's got a lot of daylight I've noticed it makes it harder to discern the issue. Again I wouldn't be complaining if this issue didn't catch my eye even when I was filming. That's how I first noticed it and dismissed it because I thought it was just the camera's monitor not acting accordingly. However I was wrong the camera's screen was right as most people have agreed with me that this issues is noticeable in Raw (before grading). Again if you're going to dismiss something that's obviously upsetting me, I'd appreciate you be completely thorough before coming to a conclusion.

If the histograms Tom has posted are correct, you are clipping information in the shadows. There is no more discussion needed as to WHY there are issues in the image.

I think you simply need to consider that you have to create your exposure differently than you are accustomed to. Each camera is different and the BMCC is no exception. Expose your image so you aren't clipping any info and you'll definitely get better results.

Most people looked at John Brawley's last images (from the beach) and thought they were overexposed, however they were exposed properly to give the most information for the scene. Don't get drawn into the fault of looking on the LCD for your image, you need to understand what information you need to capture and set the camera accordingly. The more information you can pull from each pixel, the higher the image integrity and the more you can do with the image in post.

For the record I do not have "my" camera right now, I've been using a friend's but when I do have a camera I'll help out even more so... many things that I want to test as well, and I really want to see the camera find its place in the community, so that if/when V2 hits it'll be an even stronger option...

>=P If not the obvious choice muaha.

Something else to remember, and it's not to sort of downplay anything that anyone considers an issue, but at this stage it's growing pains. Before, you wouldn't have a camera of this caliber reaching the hands of many people that weren't very experienced in the field and had already been cut by bleeding edge technology a few times.

With the ticket to ride being so low, and the product being so intricate--which I guess you could actually argue that it's not as intricate as an FS100 which does all of the work for you, a lot of people that wouldn't normally experience said growing pains will and they'll be discouraged.

The first time I got to step into that high-tech bleeding edge arena, as far as camera gear goes, was RED ONE: we shot with one of the first ones out of the gate ritually and every single problem that the camera had, I experienced. I'm talking the camera shutting off during a take, not wanting to boot up again, half of the image coming out green, so on and so forth.

This is NOTHING like that. I consider these things that BMD's working out to be akin to the 1600 grit and soap stage of a second coat for a custom car spray ... the first RED days were more like the bondo stage of restoring a beater. =X

Even with these minor knicks and dings, what the camera has to offer at this stage puts it side by side with Epic for me, and in most cases I would likely rather shoot Blackmagic anyway. Might just be me, but yeah.

sean mclennan wrote:If the histograms Tom has posted are correct, you are clipping information in the shadows. There is no more discussion needed as to WHY there are issues in the image.

BEFORE grading I have this issue. I'm not addressing after color correction. I'm not trying to pull detail out of clipped shadows. I see this from the get go and that's not acceptable.

If you're still saying this is invalid argument, how would you propose I re-shoot an establishing shot without having this issue? If i'm using the camera wrong, I'll be happy to admit it. I just want to produce a raw image that doesn't expose this problem (before grading) when shooting with available light. I don't think what I'm requesting is unreasonable. Again I'd be happy with what Kholi's getting out of his camera (When he shoots available light) so if someone can show me what I'm doing wrong, I'll be happy to shut up.

Edmond, please calm down, I really am not trying to wind you up or say you are imagining things or anything at all like that. I worded my comment very specifically to try and be clear about how our own personal criteria for what is acceptable in terms of camera performance is subjective. My "judgement" is only for myself, everyone else must decide for themselves of course, I accept and expect people to disagree with my assessment.

I downloaded your vimeo file back before I made a comment to you on this thread. I could only see it very very faintly.

From what I understand, there are slight variations in how each sensor will behave and as such each on will be calibrated slightly for each camera. This was my suggestion as to why Kohli's footage looked better - but as Christian also was able to see the same artefact kohli's dng - my overall point is that it is a characteristic of the camera, rather than it being a fault with a select few units. This is the crux of why I am posting here - I am trying to help us all ascertain whether this is a fault with specific models, or whether it is a natural characteristic of the camera. I am not trying to dismiss your claims. I simply added my own person opinion on how much of a problem it would be for me. But then again, I do not have my camera yet, so what the hell do I know :-p

My own opinion on it being within MY own tolerances are based on the following factors:1 - I currently believe it to be an inherent characteristic with all BMCC's - but albeit with slightly variable levels of severity. 2 - Considering the previous point - and that I have seen footage which does not display the effect in scenes which have been exposed differently - and you yourself have confirmed that in brighter situations the problem does not occur - It does not concern me for my own uses as I do not plan to try to film in such dark situations.

I sincerely apologise for appearing to be so dismissive of your posts, I hope I have made myself clearer now and have explained that I was speaking on behalf of my own tolerances.

I have looked at the footage on 3 different screens, 1 Large HDTV and 2 calibrated screens, I can only see the effect when really straining my eyes - and as I failed to properly express in a previous post - when grading to try and push the noise/artefact into the blacks - it vanished altogether.

I only wish to be productive in getting to the bottom of this, I have no intention of upsetting people in the process.

xD I feel like a broken record, only without the benefit of not being self aware of my repetitious babble...

The "line" that you're seeing in the DNG I shared is simply the sensor's pattern showing up. There are SEVERAL of these lines running horizontally and vertically. An easy way to spot them is to move your browser's horizontal scroll bar left to right while looking at the image, or the vertical scroll bar up and down while looking at the image.

THey're all over the place, that's the characteristic of FPN.

What Christian and Edmond are seeing? I would not categorize as fixed patterned noise. It's something completely different, and whether that's part of the design or not, does not fit the traditional description of FPN.

That is why neither examples behave the same.

Maybe it would help to root out the differences in gear being used? Power, monitors, etc?

here they are in BMCfilm: (still using the raw DNG files in resolve, without grading)

Edmonds

ScreenHunter_11 Jan. 21 19.53.jpg (58.34 KiB) Viewed 18040 times

Kohli's

ScreenHunter_12 Jan. 21 19.53.jpg (41.78 KiB) Viewed 18040 times

You are probably (big emphasis on the probably) correct, Kohli - but there does seem to be a variation in the type of light in your shot to Christians and Edmonds, do you have any other similarly lit dng's to share - preferably of similar colour temperatures/ types of lighting?

Tom wrote:Edit: Could you try shooting a few low light shots, similar to these, but at various colour temperatures and with different types of lights?

Tom thanks for your insight and I apologize if you thought I was getting hostile.

Progress is all I'm looking for and these last couple posts have been super helpful between you and Kholi. The color balance suggestion is great and I'll try to put something together tonight if I have time. Also I can shoot on my street to simulate a shot with the color temperature similar to Kholi's sample .dng and see if the results are closer to his.

Kholi I'm operating at a pretty bare bones level. I just have a rig and am still trying to figure out which additional power source to go with. As far as lenses I don't have any manual aperture lenses but I'm stopping by B+H to possibly pick up a Rokinon/Samyang 24mm T1.5 just to see if more control yields any better responses.

Thanks again, for everyone's help. Any further suggestions would be greatly appreciated

Here are a few lowlight DNG's to add to the mix. I shot these the other evening after shooting the skintone test. There was so little light that my iPhone struggles to even register an image (attached sample).

I think they were shot with a Carl Zeiss ZF.2 2/35 or a Carl Zeiss ZF.2 1.4/50.

The image of the man's face is closer to the light level of the other problematic shots, and I think I can see the same subtle variation in the image.

Here they are together, with an ev of +1 in resolve. You can see the line matches up - although I think it is less prominent on Adams sample - then again, its not ever been very clear on any of my screens, so I would be interested to see how it looks to Edmond and Christian.